Big Question for 2012: Was There Ever Life on Mars?

On Aug. 6, 2012, if all goes well, NASA's Mars Science Laboratory will touch down to tackle a new set of questions about whether there was once life on Mars.

A pair of predecessor rovers, Spirit and Opportunity, as well as a fleet of orbiting spacecraft have laid the groundwork for the mission, amassing an impressive body of evidence for past water on the surface of Mars. Those findings are key, for without water scientists aren't sure life can exist. With water, we know it's possible.

The Mars Science Laboratory, nicknamed Curiosity, is designed to nail down some specifics about the water, such as how long it existed in liquid form and whether it was too acidic to support life. But it also breaks new ground with the first studies of the Red Planet since NASA's '70s-era Viking Mars landers looked for other ingredients for life, namely organics.

Curiosity's landing site, a location near the equator known as Gale Crater, was selected after years of careful deliberation.

The 96-mile-wide crater contains a central mound of what appears to be layered sediment that stretches 3 miles high into the sky — twice the height of the walls of the Grand Canyon. The mountain might be the remains of a eroded lakebed, with the history of water — and possible remnants of life — preserved in its clays, rocks and soil.

Curiosity is not a life-detection mission, per se. Rather it is an attempt to characterize the conditions necessary for life both in the present and, more likely, the past. But scientists, who have always been surprised by findings on Mars, are trying to keep an open mind.

"We want to consider that if Tim Allen's 'Galaxy Quest' alien rock creature comes up and bangs us on the head, we don't want to ignore it," said biochemist Steven Benner, who heads the Foundation for Applied Molecular Evolution in Gainesville, Fla. "That would be the 'aha!' moment that we would regret having missed. But that's relatively far down in our what-if scenarios."

Image: Did our sun foster life on more than one planet? Sunset on Mars, as viewed by NASA's Spirit rover (2004-2010) looking out from Gusev Crater. (Credit: NASA/JPL/Texas A&M/Cornell).